Plants “smell” siblings, scale back competition

A study out in Communicative and Integrative Biology shows the mechanism behind plants that can recognize their own siblings. These plants send out fewer roots when planted next to siblings than when they’re planted next to strangers, a phenomenon the researchers think lessens competition among sibs but increases competition among unrelated plants.

The study was done in the lab of Harsh Bais, a researcher at the University of Delaware, on the common laboratory plant Arabidopsis thaliana. Bais and his graduate student Meredith Biedrzycki, the lead author on the paper, exposed seedlings to exudates, or root secretions, of siblings and of unrelated plants. The plants exposed to strangers’ exudates had greater lateral root formation — that is, their roots spread further away from the plant.

The ecologists used wild-collected strains of Arabidopsis in the study to avoid the potential of lab-reared strains having unknown siblings. It’s interesting that a well-studied lab plant would show this ability to sense its siblings. It would be interesting also to know what other wild plants have this heightened sense of family. Is it common, or specific to certain groups? Are there traits in Arabidopsis that make it a good lab plant and also give it advanced sensory capabilities?

2 Comments

I am pleased to see a blog about my work on the ESA website, however, I would like to respectfully address a few inaccuracies in the reporting.

First, although I am often guilty of anthropomorphizing plants, to say that we showed that plants can “smell” eachother in this study is a bit of a leap. We simply showed that they recognize a chemical clue released by the roots.

Also, the plants exposed to strangers’ exudates did have more lateral root production, however plants were only exposed to exudates of other plants and we never grown together. Therefore, there was no directional response in the root growth away from another plant, simply more root growth. We suspect the increase in root growth is to increase competition and resource uptake.

Our collaborator, Susan Dudley, has shown this kin recognition in her previous studies with Cakile edentula (sea rocket) and has also found a reverse outcome in several other species.

Arabidopsis is a great lab plant since it is small in size, has a short life cycle and produces large amounts of seed. It is for these traits and the genetic tools associated with a sequenced species that we choose the plant rather than for any other ecological traits.

I hope I was able to claify a few points. Please enjoy the details in our paper when it is published!

Thanks for those insights and for answering my questions, Meredith. It’s a fascinating study.

When I said the roots grew further away from the plant, I actually meant from the plant itself, not from other plants. I believe this is true with the lateral root growth…? And of course the animal sensation of smell isn’t how these plants sense chemical cues, but it’s a way to help readers relate to their sensory system under the soil.